U.S. patent application number 10/441727 was filed with the patent office on 2004-11-25 for imager cover-glass mounting.
This patent application is currently assigned to Everest VIT. Invention is credited to Schiefer, Eugene C..
Application Number | 20040233318 10/441727 |
Document ID | / |
Family ID | 33450067 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040233318 |
Kind Code |
A1 |
Schiefer, Eugene C. |
November 25, 2004 |
Imager cover-glass mounting
Abstract
Devices and methods for protecting components of imaging devices
are provided. In the illustrative embodiment, a plano-concave
protective cover is provided which is bonded to an imager window by
applying a thick, quick-setting adhesive to the exterior of the
cover and of the imager window.
Inventors: |
Schiefer, Eugene C.;
(Liverpool, NY) |
Correspondence
Address: |
WALL MARJAMA & BILINSKI
101 SOUTH SALINA STREET
SUITE 400
SYRACUSE
NY
13202
US
|
Assignee: |
Everest VIT
|
Family ID: |
33450067 |
Appl. No.: |
10/441727 |
Filed: |
May 20, 2003 |
Current U.S.
Class: |
348/335 ;
348/E5.028 |
Current CPC
Class: |
H04N 5/22521
20180801 |
Class at
Publication: |
348/335 |
International
Class: |
H04N 005/225 |
Claims
What is claimed is:
1. A cover assembly for an imager window of an imaging device, said
imaging device having a focal length, the imager window including
at least one optically active region, said cover assembly
comprising: an optically transmissive cover element having at least
one edge shaped to form a tight fit with an edge of the imager
window; and a mounting element disposed on an exterior edge of the
cover element and on an exterior edge of the imager window so as to
hold the at least one edge of the cover element to the edge of the
imager window in a tight fit, and form a seal between the cover
element and the imager window, wherein the cover element is shaped
to create an air gap between the cover element and the at least one
optically active region of the imager window.
2. The cover assembly of claim 1, wherein the cover element is
shaped in a plano-concave manner to create the air gap.
3. The cover assembly of claim 1, wherein the cover element is
shaped in a convex-concave manner to create the air gap.
4. The cover assembly of claim 1, wherein the cover element is
shaped in a concave-concave manner to create the air gap.
5. The cover assembly of claim 2, wherein the concave portion of
the cover element has a radius of curvature of about the focal
length of the imaging device.
6. The cover assembly of claim 2, wherein the concave portion of
the cover element has a radius of curvature sufficient to prevent
the formation of Newton's rings.
7. The cover assembly of claim 6, wherein the concave portion of
the cover element has a radius of curvature which is greater than
the focal length of the imaging device.
8. The cover assembly of claim 1, wherein the cover element is
shaped to create an air gap sufficient to prevent the presence of
Newton's rings.
9. The cover assembly of claim 1, wherein the mounting element is
selected from the group of mounting elements consisting of:
adhesives, tapes, shrink tubes, and mechanical mountings.
10. The cover assembly of claim 1, wherein the mounting element is
an adhesive.
11. The cover assembly of claim 10, wherein the adhesive is an
epoxy.
12. The cover assembly of claim 11, wherein the adhesive is a
fast-curing epoxy.
13. The cover assembly of claim 10, wherein the adhesive is
thick.
14. The cover assembly of claim 1, wherein the imager window is
part of an electronic-type imaging device.
15. The cover assembly of claim 14, wherein the imager window is
part of a CCD-type imager.
16. The cover assembly of claim 14, wherein the imager window is
part of a CMOS-type imager.
17. The cover assembly of claim 1, wherein the imager window is
part of an imaging device selected from the group of imaging
devices consisting of: microscopes, camcorders, thermal imagers,
telescopes, digital cameras, endoscopes, and boroscopes.
18. The cover assembly of claim 1, wherein the cover element is
constructed from a material selected from group of materials
consisting of: glass, plastics, crystals, and composites.
19. A cover assembly for an imager window of an imaging device
comprising: a cover element having at least one edge shaped to form
a tight fit with an edge of the imager window; and a layer of
adhesive disposed on a peripheral edge of the cover element and on
a peripheral edge of the imager window so as to hold the at least
one edge of the cover element to the edge of the imager window, and
form a seal between the cover element and the imager window,
wherein the cover element is oriented so that a portion of the
cover element creates an air gap between the cover element and the
imager window.
20. The cover assembly of claim 19, wherein the cover element is
plano-concave, convex-concave, or concave-concave.
21. The cover assembly of claim 19, wherein the adhesive is
epoxy.
22. The cover assembly of claim 19, wherein the imager window is
chosen from the group of imager windows consisting of: windows,
lenses, and CHL assemblies.
23. The cover assembly of claim 19, wherein the air gap is of
sufficient size to prevent the presence of Newton's rings.
24. The cover assembly of claim 19, wherein the cover element is a
lens.
25. A method for protecting an imager window of an imaging device,
comprising the steps of: providing an optically transmissive cover
element having at least one exterior edge; applying a mounting
element to an exterior edge of the cover element and to an exterior
edge of the imager window, wherein the cover element is shaped to
create an air gap between the cover element and the imager window,
and wherein the mounting element forms a seal over the exterior
edge of the cover element and the exterior edge of the imager
window.
26. The method of claim 25, wherein the cover element is of
plano-concave, concave-concave, or convex-concave.
27. The method of claim 25, wherein the mounting element is
selected from the group of mounting elements consisting of:
adhesives, tapes, shrink tubes, and mechanical mountings.
28. The method of claim 25, wherein the presence of the air gap
prevents the creation of Newton's rings.
29. The method of claim 25, wherein the imaging device is selected
from the group of imaging devices consisting of: microscopes,
camcorders, thermal imagers, telescopes, digital cameras,
endoscopes, and boroscopes.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] None.
[0002] 1. Field of the Invention
[0003] The invention relates generally to protective covers for
imaging devices.
[0004] 2. Background of the Invention
[0005] Electronic-type imaging devices of the type used, for
example, in microscopes, telescopes, camcorders, thermal imagers,
digital cameras, and especially with digital inspection systems
(e.g., borescopes, and endoscopes), often are subjected to harsh
physical operating conditions, and must embody a degree of
survivability, in terms of mechanical durability, temperature
tolerance, etc., which exceeds that required for similar
electronics designed to operate in more benign environments, such
as in clean rooms and climate-controlled office environments. In
addition, these "hearty" imaging devices must be protected against
environmental debris, such as dirt, dust, chemicals, and corrosive
fluids, which might damage the optical elements (typically located
in a tip of the imaging device) associated with the imaging devices
introduced into hostile environments. "Optical elements" include
well-known components used in imaging devices, such as miniature
electronic image sensors (of the type, for example, used in
CCD-type or CMOS-type imagers), mirrors, light sources (such as
LEDs and laser diodes), and lenses.
[0006] In the past, windows, lenses, CHL assemblies, or other
imaging portals leading to the optical elements of an imager
(hereinafter, "imager window") located in a tip of an imaging
device have been afforded a modicum of protection by affixing a
flat, optically transmissive element onto the imager window, such
as a flat glass disk or plate. The flat element typically is bonded
to the imager window using a UV adhesive, i.e., an adhesive cured
under ultraviolet light during manufacturing. UV adhesives
typically are used because of their generally quick cure times
which, in turn, allow for a relatively short manufacturing step
associated with the bonding.
[0007] This method of protecting the imager window, however,
creates certain disadvantages with regard to the operation of the
imaging device. For example, the use of a flat optical element
bonded to an imager window, with UV adhesive interposed between the
optical element and the imager window, gives rise to Newton's
rings, a phenomenon observed when two materials with differing
refractive indices are in close contact with each other. In
practice, the presence of these rings (which typically are a series
of concentric rings surrounding a central dark spot) reduces the
image quality produced by the imaging device. Furthermore, the UV
adhesives used to bond the flat optical element to the imager
window, when stressed mechanically or thermally, tend to fail and
crack, creating unwanted distortions and artifacts in the image
produced by the imaging device. The failure of these adhesives also
allows the flat optical element to disengage from the imager
window, losing any protective benefit conferred by the presence of
the flat optical element.
[0008] One prior art approach to addressing these problems has been
to interpose bonding pads between the optical element and the
imager window, and then to bond the optical element to the bonding
pad in such a manner as to create a seal between the bonding pad
and the optical element. That approach, however, is disadvantageous
in that it requires additional materials and time-consuming
alignment and bonding steps with regard to the bonding pads.
[0009] Another prior art approach has been to interpose adhesive,
in the form of strips of preformed thermoplastic or thermosetting
adhesives, between the optical element and the imager window at the
edges where the optical element and imager window contact each
other. However, this approach also is flawed in that the preformed
adhesive strips cannot be tightly controlled when melted under
heat, allowing the adhesive to "run" into the viewing area of the
imager window.
SUMMARY OF THE INVENTION
[0010] It is the object of this invention to provide a cover for an
imager window assembly which overcomes the disadvantages of prior
art methods of protecting the imager window.
[0011] In one aspect of the invention, an imager window cover
assembly is provided including an optically transmissive cover
element mounted to an imager window by means of a mounting element
applied to the exterior of the imager window cover and the imager
window so that light traveling toward an imager window does not
pass through the mounting element.
[0012] In another aspect of the invention, an imager window cover
assembly is provided which eliminates image distortion attributable
to Newton's rings.
[0013] In another aspect of the invention, an imager window cover
assembly is provided which does not create visual distortion upon
failure of an adhesive.
[0014] In a further aspect of the invention, an imager window cover
assembly is provided which is less likely than prior art imager
window covers to disengage from the imager window.
[0015] In yet another aspect of the invention, an imaging device is
provided with an imager window cover element which protects optical
elements of the imaging device from adverse environmental
conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an imaging device according to the invention;
[0017] FIG. 2 is an enlarged view of a distal end of the imaging
device of FIG. 1;
[0018] FIG. 2A is an enlarged view of the distal end of FIG. 2;
and
[0019] FIG. 3 is a side perspective view of an imager window cover
element according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] It is to be understood that the invention is not limited in
its application to the details of construction and arrangements of
components set forth herein in the detailed description of the
preferred embodiment or illustrated in the drawings. The invention
is capable of other embodiments and of being practiced or being
carried out in various ways.
[0021] Referring to FIG. 1, a typical imaging device 100 (a
boroscope in the illustrative embodiment) according to the
invention is illustrated, such as is sold by Everest VIT.RTM. of
Flanders, N.J. Such a device could include, as shown in the
illustrative embodiment, a portable shipping/operating case 110,
that includes a power supply 120 for the device and a light source,
such as a metal halide arc lamp (not shown). The shipping/operating
case 100 is shown in operative communication with a handpiece 140
by means of a cable 130. The handpiece 140 can include, by way of
example, an LCD monitor 150 (which displays images seen by the
imaging device), a joystick control 145 (for articulating a distal
end 170 of the imaging device 100), and a button set 143 (for
accessing measurement, digital, and measurement controls associated
with the imaging device 100). The handpiece 140 also is connected
to an insertion tube 160, which terminates in a distal end 170. As
used herein, the term "distal" shall mean "in the direction of the
tip of the boroscope, furthest from the handpiece 140." The
insertion tube 160 can be sized according to the desired
application, by varying a diameter and a length of the insertion
tube 160. The insertion tube 160 can include, for example, a
durable tungsten braid overlaying a stainless steel monocoil for
crush resistance, and one or more layers of a polyurethane sealant
for protection from liquids and vapors. The interior of the
insertion tube 160 (not shown) can include standard imager lines
and communication/control means, such as fiber-optic cables and
articulation wires.
[0022] An enlarged view of the distal end 170 of the imaging device
100 described herein is illustrated in FIG. 2. The distal end 170
includes a camera housing 210 surrounding a camera assembly
comprising, in the illustrative embodiment, an objective window
250, an aperature 240, an acromat 230, a light baffle 220, and an
imaging assembly 225. Such camera assemblies (without the inventive
cover assembly) are well-known, and commercially available from the
Semiconductor Business Division of Sony Electronics Inc.
[0023] An enlarged view of the imaging assembly 225 is shown in
FIG. 2A. The imaging assembly generally includes an imager cover
element 270 (described in greater detail in relation to FIG. 3) and
a CHL assembly 260. As used herein, "CHL" is an acronym for "Chip
Hybrid Lead", which refers generally to a imager ("chip"), the
electronics which amplify the signal from the imager ("hybrid"),
and a harness which carries the imager signal back to an imaging
device ("lead"). The cover element 270 is fitted to the CHL
assembly 260 by a mounting element 280. In the illustrative
embodiment, the mounting element 280 is shown as an adhesive
portion deposited in a bead-like pattern on a peripheral, exterior
edge of imager cover element 270 and an exterior edge of CHL
assembly 260 in the illustrative embodiment of FIG. 2A. One of
ordinary skill will appreciate, however, that the mounting element
could comprise, instead of adhesive, tapes (such as MYLAR.RTM.
tape), shrink tubes, and mechanical mountings. In the illustrative
embodiment, the mounting element 280 (which shall be referred to as
an "adhesive portion" in connection with the illustrative
embodiment) preferably is a thick adhesive, to prevent the adhesive
from being interposed between (or "running" into) the space between
the imager cover element 270 and the CHL assembly 260 during
manufacture. By "thick" what is meant is an adhesive having a
viscosity of between about 100,000 centipoise and about 1,000,000
centipoise. The prevention of, and lack of, adhesive (or any other
desired mounting element) between the imager cover element 270 and
the CHL assembly 260 is an important feature of the invention, as
adhesive between the two might crack (leading to degraded image
quality) or fail (leading to loss of the imager cover element
270).
[0024] The imager cover element 270, as illustrated in FIG. 2A and
FIG. 3, is shaped to create an air gap 275 between the imager cover
element 270 and the CHL assembly 260. This air gap provides a
sufficient distance so that the imager cover element 270 and the
CHL assembly 260 are not close enough for any differences in their
respective refractive indices to give rise to Newton's rings.
[0025] The adhesive portion 280 also preferably is a quick-cure
adhesive, so that the application of the adhesive portion 280 does
not become a time-consuming step during the manufacture of the
imaging assembly 225. By "quick" what is meant is an adhesive that
is cured within about 15 minutes of application. Generally, epoxy
adhesives, and in particular HYSOL.RTM. 608, offered by Loctite
Corporation, have been found to be a well-suited for the purposes
of bonding the imager cover element 270 to the CHL assembly
260.
[0026] Referring to FIG. 3, the imager cover element 270 is shown,
in the illustrative embodiment, to have a plano-concave shape,
though the invention equally may be practiced using other shapes,
such as convex-concave or concave-concave. In the illustrative
embodiment, the imager cover element 270 has a distal, non-imager
facing side 320, which is shown as being planar, and a proximal,
imager facing side 310, which is shown having a concave indentation
315. The concave indentation 315, when paired with the CHL assembly
260, creates the tight fit as well as the air gap 275 defined
between the imager cover element 270 and the CHL assembly 260, as
shown in FIG. 2A. The concave indentation 315 prevents the
formation of Newton's rings by preventing a surface to surface
orientation between the imager cover element 270 and the viewable
area of the CHL assembly 260, as is seen in (prior art) cover
assemblies employing a flat cover element. The concave indentation
315 also serves to prevent the externally applied adhesive portion
from being drawn into the air gap 275 by means of capillary action.
In the illustrative embodiment, the indentation 315 can be
described by a radius of curvature 330 which is about equal to the
focal length of the imaging device 100 (which in the case of the
illustrative boroscope is about 3.00 mm+/-0.03 mm). The radius of
curvature, however, is not a vital feature of the present
invention, and any radius of curvature between the focal length of
the device and infinite could be used, so long as enough of the air
gap 275 is maintained to prevent the formation of Newton's
rings.
[0027] The imager cover element 270 is achromatic in the
illustrative embodiment, though the imager cover element could be
pigmented or otherwise treated to filter out certain wavelengths of
light if desired. If desired, the imager cover element 270 also
could be machined to provide an additional, optical modification of
light coming entering the CHL assembly 260, i.e., the imager cover
element 270 could act as a lens. The imager cover element 270 could
be fabricated from any desired, optically-transmissive material,
such as glass, plastic, crystal, or composites suitable for optical
uses. Notably, the short distance between the imager cover element
270 and the CHL assembly 260 ensures that any environmental debris
that is deposited on the distal end 320 of the imager cover element
270 remains out of focus, and does not materially alter any image
that is subsequently generated by the CHL assembly 260.
[0028] The imager cover element 270 is shaped so that the edges of
the cover element sealingly engage the edges of the CHL assembly
260 to form a tight fit. By "tight," what is meant is that the
edges are shaped in a manner so that when the adhesive portion 280
(or other selected mounting element) is applied to the exterior of
cover element 270 and the CHL assembly 260, as shown in FIG. 2A,
the adhesive portion 280 (or other selected mounting element) is
unable to enter the air gap 275. After the adhesive portion 280
sets, a seal is formed comprising the adhesive portion 280, and the
tight fit between the edges of the imager cover element 270 and the
CHL assembly 260, preventing environmental debris from entering the
air gap 275 and affecting the CHL assembly 260.
[0029] While the invention has been described in conjunction with a
preferred embodiment, it is evident that numerous alternatives,
variations, and modifications will be apparent to those skilled in
the art in light of the foregoing description. Thus, it is
understood that the invention is not to be limited by the foregoing
illustrative details.
Equivalents
[0030] While the invention has been particularly shown and
described with reference to specific embodiments, it should be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the invention as defined by the appended claims.
* * * * *